Traumatic brain injury is a major cause of death and disability and is frequently associated with the failure of cerebral blood vessels. However, little is known about the biomechanics of these vessels. The long-term goal of this research is to determine the contribution of the cerebral blood vessels to the mechanical response of the brain and to develop more effective tools and strategies for the prevention of traumatic brain injury. Recent work by our group has defined the longitudinal mechanical properties of human cerebral arteries and veins. A preliminary finite element model incorporating these data suggests that the cerebral blood vessels constrain brain deformations. The central hypothesis of this proposal is that the cerebral blood vessels and the surrounding pia-arachnoid complex significantly contribute to brain tissue deformation and failure. Three aims are proposed to test this hypothesis. Aim 1 will delineate the mechanical behavior of cerebral vessel branch points to determine if they are more susceptible to deformation and failure than unbranched sections. Aim 2 will characterize the mechanical behavior of the pia-arachnoid complex to determine its influence on cerebral vessel response and failure. Aim 3 will define tissue deformations in the proximity of a branched blood vessel through both physical and numerical modeling to determine if branched vessel structure provides additional constraint to surrounding brain tissue in comparison to straight vessel segments alone. The proposed research should provide definitive data regarding the influence of cerebral blood vessels and the pia-arachnoid complex on brain tissue deformation and failure. If these structures are proven to be important, as anticipated, their inclusion in a more clinically relevant finite element model could lead to more effective injury protection systems and pave the way for improved prevention and outcome of traumatic brain injury.